NASA Cassini Significant Events for 01/23/2013 - 01/29/2013

Cassini is orbiting Saturn with a period of 13.3 days in a plane inclined 53 degrees from the equatorial. The most recent spacecraft tracking and telemetry data were collected on Jan. 30 by a 34 meter Deep Space Network station at Canberra, Australia. Except for some science instrument issues described in previous reports, the spacecraft continues to be in an excellent state of health with all of its subsystems operating normally.

Sequence Implementation Process teams continued working on the ten-week command sequences S78 and S79, which will go active on Cassini in March and June respectively, and planning continued for the 2016 start of Cassini's F-ring and Proximal Orbits phase. Meanwhile, commands from the on-board S77 sequence controlled the spacecraft's activities in flight. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" page at: http://saturn.jpl.nasa.gov/mission/presentposition/ .

A calibration of Cassini's Y-thrusters took place today. This annual exercise allows the Navigation and Attitude Control teams to validate the force-balance of the coupled Y-thruster pairs. Preliminary navigation results were as expected. This is an important measurement because Reaction Wheel Assembly (RWA) bias maneuvers using the Y-thrusters are performed frequently, and are not tracked by the Deep Space Network (DSN). Three such RWA bias maneuvers were done this week, including one today right before the calibration.

The Visible and Infrared Mapping Spectrometer (VIMS) began making a 12 hour mosaic of the dark side of the rings. On most occasions such as this, optical remote-sensing observations led by one instrument include "ride-along" data-taking by other optical instruments since their boresights are co-aligned.

After 14 years of exceptional management of the Cassini-Huygens Program, Bob Mitchell retired today; Dr. Earl Maize has returned to become the new Program Manager. Maize managed the Cassini Spacecraft Operations Office through assembly and test, launch and early cruise, and later served as the Deputy Program Manager up through the Huygens touchdown on Titan.

Friday, Jan. 25 (DOY 025)

The Imaging Science Subsystem (ISS) performed an observation in the satellite orbit campaign, then the Navigation team used ISS to take five images of Saturn's satellite Rhea against background stars for optical navigation purposes. The Composite Infrared Spectrometer (CIRS) began a 22 hour observation to measure oxygen compounds (H2O, CO2) in Saturn's stratosphere.

Cassini passed through apoapsis, having coasted just over 1.7 million kilometers "up" from the planet and slowing to 10,892 kilometers per hour relative to Saturn. This marked the beginning of Cassini's orbit #180.

Saturday, Jan. 26 (DOY 026)

VIMS began a 13.5 hour observation of the star R Lyrae as it was being occulted by the rings.

Sunday, Jan. 27 (DOY 027)

ISS began a 13 hour low-resolution movie of the F ring. DSN stations in Canberra, Australia and Goldstone, California participated in two operations readiness tests today, and two more on Monday, preparing for the radio science ring and Saturn atmosphere occultation experiment coming up on Thursday.

Monday, Jan. 28 (DOY 028)

Today and again on Tuesday, ISS created movies of the dark face of the rings lit from behind at high phase, in order to search for periodicities in the spokes. CIRS then began an eight hour observation of the main rings in order to obtain compositional information.

The Magnetometer executed a calibration by rolling the spacecraft about its Z axis during a DSN communications session.

The flight team processed Orbit Trim Maneuver (OTM) #339 and approved its command file for uplink tonight; it will execute on Jan. 30. OTM #339 will be a main engine burn of about 1.66 m/s targeting the Titan flyby T89 occurring on February 16 (PST).